The present invention relates to an illumination device for simulating neon lighting using high-intensity, low-voltage light sources, an illumination device ideally adapted for lighting, signage and advertising uses.
Neon lighting, which is produced by the electrical stimulation of the electrons in the low-pressure neon gas-filled glass tube, has been a main stay in advertising and for outlining channel letters and building structures for many years. A characteristic of neon lighting is that the tubing encompassing the gas has an even glow over its entire length irrespective of the viewing angle. This characteristic makes neon lighting adaptable for many advertising applications, including script writing and designs, because the glass tubing can be fabricated into curved and twisted configurations simulating script writing and intricate designs. The even glow of neon lighting being typically devoid of hot spots allows for advertising without visual and unsightly distractions. Thus, any illumination device that is developed to duplicate the effects of neon lighting must also have even light distribution over its length and about its circumference. Equally important, such lighting devices must have a brightness that is at least comparable to neon lighting. Further, since neon lighting is a well-established industry, a competitive lighting device must be lightweight and have superior “handleability” characteristics in order to make inroads into the neon lighting market. Neon lighting is recognized as being fragile in nature. Because of the fragility and heavy weight, primarily due to its supporting infrastructure, neon lighting is expensive to package and ship. Moreover, it is extremely awkward to initially handle, install, and/or replace. Any lighting device that can provide those previously enumerated positive characteristics of neon lighting, while minimizing its size, weight, and handleability shortcomings, will provide for a significant advance in the lighting technology.
The more recent introduction of lightweight and breakage resistant point light sources, as exemplified by high-intensity light-emitting diodes, have shown great promise to those interested in illumination devices that may simulate neon lighting and have stimulated much effort in that direction. However, the twin attributes of neon lighting, uniformity and brightness, have proven to be difficult obstacles to overcome as such attempts to simulate neon lighting have largely been stymied by the tradeoffs between light distribution to promote the uniformity and brightness. For example, U.S. Pat. No. 4,976,057 issued Dec. 11, 1990 to Bianchi describes a device that includes a transparent or translucent hollow plastic tubing mounted in juxtaposition to a sheet of material having light transmitting areas that are co-extensive to the tubing. The sheet is backlit by light sources such as LEDs which trace the configuration of the tubing. The tubing can be made into any shape including lettering. While the tubing may be lit by such arrangement, the light transfer efficiencies with such an arrangement is likely to result in a “glowing” tube having insufficient intensity to match that of neon lighting. The use of point light sources such as LEDs may provide intense light that rival or exceed neon lighting, but when arranged in arrays, lack the uniformity needed and unfortunately provide alternate high and low intensity regions in the illuminated surfaces. Attempts to smooth out the light have resulted in lighting that has unacceptably low intensity levels.
In an attempt to address some of the shortcomings of neon, commonly assigned U.S. Pat. No. 6,592,238, which is incorporated in its entirety herein by reference, describes an illumination device comprising a profiled rod of material having waveguide properties that preferentially scatters light entering one lateral surface (“light-receiving surface”) so that the resulting light intensity pattern emitted by another lateral surface of the rod (“light-emitting surface”) is elongated along the length of the rod. A light source extends along and is positioned adjacent to the light-receiving surface and spaced from the light-emitting surface a distance sufficient to create an elongated light intensity pattern with a major axis along the length of the rod and a minor axis that has a width that covers substantially the entire circumferential width of the light-emitting surface. In a preferred arrangement, the light source is a string of point light sources spaced a distance apart sufficient to permit the mapping of the light emitted by each point light source into the rod so as to create elongated and overlapping light intensity patterns along the light-emitting surface and circumferentially about the surface so that the collective light intensity pattern is perceived as being uniform over the entire light-emitting surface.
One of the essential features of the illumination device described and claimed in U.S. Pat. No. 6,592,238 is the uniformity and intensity of the light emitted by the illumination device. While it is important that the disadvantages of neon lighting be avoided (for example, weight and fragility), an illumination device would have little commercial or practical value if the proper light uniformity and intensity could not be obtained. This objective is achieved primarily through the use of a “leaky” waveguide rod. A “leaky” waveguide is structural member that functions both as an optical waveguide and light scattering member. As a waveguide, it tends to preferentially direct light entering the waveguide, including the light entering a lateral surface thereof, along the axial direction of the waveguide, while as a light scattering member, it urges the light out of an opposite lateral surface of the waveguide. As a result, what is visually perceived is an elongated light pattern being emitted along the light-emitting lateral surface of the waveguide.
As described in U.S. Pat. No. 6,592,238, certain acrylics, polycarbonates, and epoxys have the desired preferential light scattering properties needed to produce a leaky waveguide; for example, one such acrylic material is commercially available from AtoHaas, Philadelphia, Pa. under order number DR66080. These compounds are extremely lightweight and are able to withstand rough shipping and handling. These compounds can be easily molded or extruded into a desired shape for a particular illumination application and thereafter heated and bent to a final desired shape or shapes. However, because of these desirable attributes, these compounds are not inexpensive.
Fluorescent lighting is similar in operation to neon lighting and therefore suffers from some of the same shortcomings as neon lighting. Specifically, fluorescent lighting also is based on the electrical stimulation of a gas in a glass tube. However, the low-pressure mercury vapor that is in the glass tube emits ultraviolet light when ionized. This ultraviolet light contacts a phosphor coating on the inside surface of the glass tube, causing the emission of visible light. Nevertheless, because of its similar construction, fluorescent lighting is also fragile and thus inappropriate for certain applications.
It is therefore an object of the present invention to provide an improved illumination device that serves as an alternative to neon lighting with all the benefits of devices made from known compounds having desired light scattering properties needed to produce a leaky waveguide, but with the additional benefit of reduced expense.
It is a further object of the present invention to provide an improved illumination device that serves as an alternative to fluorescent lighting.
These and other objects and advantages of the present invention will become readily apparent and addressed through a reading of the discussion below and appended drawings.